Supersonic compressor



Sept. 23, 1958 M. w. BEARDSLEY suPERsoNIc COMPRESSOR 2 Sheets-Sheet 1Filed May 29, 1948 www 4%. o. om bww QQ oN N l l \NN. w. N.. m. IM, MN.www Nv A Y h Il o 0 mv mu 0 0 0 v 0 0 1o 0 0 Q OAN Nm 8 mm .Nlx Tl.fknrnwh 1N r Sept. 23, 1958 M. w. BEARDSLEY suPERsoNIo COMPRESSOR 2Sheets-Sheet 2 Filed May 29, 1948 INVENTOR.

TTOENEI United States Patent C SUPERSONIC COMPRESSOR Melville W.Beardsley, Venice, Calif.

Application May 29, 1948, Serial No. 29,971 s Claims. (ci. 23o- 114) Myinvention relates generally to fluid compressors and more particularlyto such compressors which are adapted to deliver compressed gas at yarelatively high rate of flow with a relatively low ratio of compressionas compared to expansi'ble chamber type compressors. The novelcompressor described herein is, however, capable of higher compressionratios than the conventional centrifugal compressor While maintainingthe relatively high rate of liow of the centrifugal type.

The high iioW type of compressor just described is used, for example, tocompress air prior to its introduction into the combustion chamber of ajet propulsiony engine. While the compressor embodying my invention isillustrated herein as used in connection with a turbojet engine, it willbe realized by those skilled in the art that the usefulness of myinvention is not confined to such engines, but has wide application inother fields, for example, in the compressing of air for industrialuses, in the tiring of various types of furnaces, in the rst stages ofapparatus for producing liquitied gases, and in many other fields.

Basically, turbo-jet reaction engines comprise a compressor, acombustion chamber into Which the compressed air delivered by saidcompressor is introduced together with a liquid or gaseous fuel, a gasturbine actuated by the combustion products exhausting from saidcombustion chamber, and a jet or tail pipe for exhausting the combustionproducts after passing through said turbine and for producing thedesired reactive jet. The turbine provides the power to drive thecompressor.

Conventional practice in the design of turbo-jet engines has been toemploy either centrifugal or axial flow compressors, directly driven, ordriven through a gear train by the gas turbine. Briefly, the centrifugalcompressors employed in engines of the type described employ arelatively rapidly rotating rot-or and a set of stationary diffuserblades located surrounding the periphery of the rotor and adapted toconvert the kinetic energy of the centrifugally accelerated air intocompression thereof.

The axial ii-ow compressor comprises essentially an alternating seriesof rotating and stationary blades, alternately inclined whereby to forcethe air in an axial direction through the compressor, the stationaryblades serving as diiusers and to compress the air.

Both of the above described types of compressors have certaindisadvantages,4 the centrifugal type having a relatively low efliciency,and the axial liow type being extremely intricate and diliicult todesign and construct. The entrance and exit velocities of gas owingthrough both the radial (centrifugal) and axial flow compressors haveusually been less than the velocity of sound, i. e., at velocities of aMach number less than 1.0.

It is well known that a compressible fluid moving through a conduit atrates well below Mach 1.0 reacts in accordance with Bernoullis theoremwhen encountering a constriction, i. e., the pressure of the uiddecreases as the cross-sectional area of the conduit decreases. Con-"ice versely, as the conduit cross-section increases, the pressure ofthe moving fluid increases. 'This change in pressure is due to the factthat, in order for the fluid to all pass through the conduit, therelative velocities of the iiuid in various parts of the conduit mustdiffer, the velocity being greatest at the throat or most constrictedportion of the conduit.

At huid velocities of greater than Mach 1.0, however, the Bernoullibehavior is essentially reversed. That is, the pressure of the gasincreases and the velocity decreases as the cross-sectional area of theconduit becomes less.

This principle is made use of in the ram jet reactive engine of the typedesigned to move at velocities greater than Mach 1.0. Here thecompressor comprises simply a forwardly facing constricted opening, andthe result of the forward motion of the engine is to compress the airentering through the forwardly facing opening.

It will -be seen first of all that if a centrifugal compressor capableof accelerating air to a velocity greater than Mach 1.0 were designedand a set of stationary difusers placed around the periphery of therotor and into which the air was centrifugally discharged from therotor, the device would serve to reduce the velocity and compress theair thus discharged. The essential difficulty with the arrangement justdescribed is, however, that in order to produce a rotor capable ofaccelerating air to supersonic velocities, the extreme centrifugalstresses encountered present nearly insurmountable dili'iculties.

It will be realized, however, that the behavior of gases moving throughconduits is essentially due to the relative motion between the gas andthe conduit Walls. Thus, if a converging conduit is moved at a velocityover Mach 1.0 through stationary air, the result is to compress the airentering the conduit as in the ram jet engine above described.Compression is also the result if air moving at a velocity over Mach 1.0is introduced into a stationary conduit. Ergo, the same result isachieved if the sum of the velocities of a conduit moving throughoppositely moving air is greater than Mach 1.0. My novel compressoremploys the last described principle.

Briefly described, I employ a pair of counter-rotating impellers,coaXially arranged, the innermost rotor acting in the manner of -aconventional centrifugal blower to radially and tangentially accelerateair passing therethrough. From the inner irnpeller the air is dischargedin a generally tangential direction into the blades of the outer rotor(hereinafter called diffuser rotor) which, as previously stated, ismoving in a direction counter to the impeller rotor. The blades of thediffuser rotor are centrally thickened so that the passage between eachpair of successive blades has an essentially converging-diverg ing orVenturi shaped constriction.

Bearing in mind the foregoing discussion, then, it is a major object ofmy invention to provide a iiuid compressor having, relatively, a muchgreater eiciency than can be achieved in conventional centrifugalcompressors.

Another object of my invention is to provide a compressor `of the classdescribed which is capable of a higher ratio of compression than can beachieved in conventional rotary compressors.

It is a further object of my invention to provide a rotary compressor inwhich the rotating members turn at a relatively low rate whereby toavoid extreme centrifugal stresses.

A still further object of my invention is to provide a compressor of theclass described which is well adapted for use in connection withreaction jet engines for aircraft.

The foregoing and other objects and advantages of my invention willbecome apparent from a consideration of the following detaileddescription of one embodiment thereof, such consideration being givenalso to the accompanying drawings, in which:

Figure l is a partially sectioned, elevational view taken through aturbo-jet engine embodying a compressor according to my invention;

Figure 2 is a horizontal section taken on the line 2-2 of Figure 1;

Figure 3 is an enlarged elevational section of a portion of the deviceillustrated in Figure l;

Figure 4 is an enlarged elevational section take on the line 4 4 inFigure 1;

Figure 5 is a fragmentary elevational section taken on the line 5 5 inFigure l;

Figure 6 is an elevational section taken on the line 6 6 in Figure 1;and

Figure 7 is an enlarged elevational section taken on the line 7 7 inFigure 6.

Throughout the drawings, the reference character 1G identifies a mainrotary shaft turning in the direction indicated by the surrounding arrowin Figure l. The shaft 10 is supported for rotation in a pair of radialball bearings 11 and 12. The rearward bearing 11 is secured in asuitable recess 13 in a frame 14, and the forward bearing 12 issupported within non-rotating collar member 15, the nature of, and thesupport for which will be hereinafter described.

Secured to the forward end of the shaft 10 by means of a taper stub anda nut 21 is a multiple bladed impeller 22 having eight radial blades 23.

A diffuser rotor 25 is rotatably mounted on the forward end portion ofthe shaft 10 and is coaxially positioned with respect to the impeller22. The rotatable mounting of the diffuser rotor 25 is provided by apair of ball bearings 26 and 27. A number of collars 28, 29 and 30,positioned on the shaft 16 between the impeller 22, the bearings 26, 27and 12, serve to separate and prevent axial displacement of thebearings, being held against a shoulder 31 in the shaft 10 by theforward attachment nut 21.

Surrounding the impeller 22 and the diffuser rotor 25 is a stationaryhousing or manifold 40, which is horizontally divided as indicated bythe reference character 41 in Figure 5 whereby the housing 40 may beassembled over the impeller 22 and the diffuser rotor 25 after thelatter have been assembled onto the shaft 10. The housf ing 40 issecured to the frame 14 by means of a number of bolts 42. An outwardared portion 43 in the housing 4t) is secured by suitable flanges to therearward end of an air-induction conduit 44.

Eight combustion chambers 50 are mounted circumferentially around theaxis of the shaft 10, being supported at their forward ends by suitableanges secured to the housing 40 and at their rearward ends by suitableflanges secured to the frame 14. Each of the combustion charnbers 50includes an interior liner member 51 welded by a skirt-like projectionat its rearward end to the wall of the chamber 50. The liner member 51in each of the combustion chambers 50 is provided with a number ofapertures 52 through which air passes inwardly into the interior of theliner 51.

Atomized liquid fuel is introduced at the forward end of the linermember 51 by means of a nozzle 53, combustion taking place inside theliner. Since the principles of combustion and jet propulsion are notinvolved in my invention, a detailed description of the engine per se isnot felt to be necessary herein.

A double walled frusto-conical conduit is secured by a suitable flangeto the frame 14 and serves to conduct the products of combustion fromthe combustion charnbers 50 rearwardly, exhausting the same through asuitable jet pipe 56 provided at its rearward end with an inturned lipportion 57. The inner and outer walls of the conduit 5 5 are separatedby suitably positioned and streamlined radial struts 58.

Secured to the rearward end of the shaft 10 is a turbine wheel 60 havinga number of streamlined radial blades 61 at its outer periphery whichare interposed in the stream of combustion products exhausting from thecombustion chamber 50. A series of stator blades 62 are provided justahead of the turbine blades 61, the stator blades beingcounter-inclined, as indicated in Figure 2, serving the additionalpurpose of supporting the outer portion 63 of the frame 14.

As has been previously described, it is desired that the diffuser rotor25 rotate in the opposite direction from that of the impeller 22. Tothis end, a reversing gear train is provided which comprises a largebevel gear 65 keyed to the shaft 10 immediately behind the shoulder 31,a series of small bevel idler gears 66, supported between the frame 14and the collar member 15, and a forward large bevel gear 67 bolted tothe rearward surface of the diffuser rotor 25. The bearings for theidler gears 66 include roller bearings 68 xed in the collar member 15and ball bearings 69 secured in the frame member 14, as illustrated inFigure 7. A number of radial bores 70 are provided in the frame 14through which the shaft 71 of each of the idler gears 66 may beassembled. It will be noted that the radial shafts 71 Serve to supportthe collar member 15.

Thus it will be seen that the direction of rotation of the impeller 22is clockwise, while the direction of rotation of the diffuser rotor 25is counter-clockwise, as indicated in Figure 5.

In order to initiate the flow of air through the impeller 22 whenstarting the compressor, it is, in some instances, necessary to relievethe pressure in the throat of the diffuser rotor 25 until the rate ofair llow through the compressor approaches certain critical velocities,as will be hereinafter described. To this end, an annular manifoldchamber 75 is formed in the housing 40 and communicated with the annulararea adjacent the throat of the diffuser 25 by a number of passages 76,as shown in Figure 3. A number of spring-loaded valves 77 are providedat intervals around the manifold 75 whereby to relieve the initialpressure in the manifold 75 until the flow of air through the compressorreaches or approaches critical rates as will be hereinafter described.

For a discussion of the behavior of the air passing through thecompressor, reference should now be had to Figure 4. Here a portion ofthe outer periphery of the impeller 22 is shown, having thereon theouter end of one of the impeller blades 23. A portion of the diffuserrotor 25 is also shown in Figure 4, together with an adjacent pair ofdiffuser blades 80, the latter being supported on the body of thediffuser rotor 25 and projecting forwardly therefrom.

As can be seen best in Figure 4, each of the diffuser blades 80 isthickened in a portion generally midway between its ends whereby toproduce a constriction point 81 on the leading surface of each `blade8). Thus the passage between each pair of successive blades has agenerally hour-glass shape, being narrowest at a point adjacent theconstriction point 81.

Air discharged from the impeller 22 enters the space between thediffuser blades 80 in a direction indicated by the line 83 in Figure 4.The line 83 represents the direction of the resultant vector derivedfrom the relative radial and tangential velocities of the air exitingfrom the impeller 22. The velocity of the air in the direction indicatedby the arrow 83 is somewhat less than Mach 1.0.

The speed of the diffuser rotor 25 is such that the sum of the velocityof the air indicated by the arrow 83 and the tangential Velocity of thediffuser blades 80, as shown by the arrow 90, is in the resultantdirection of the arrow 91, and is somewhat greater than Mach 1.0. Thusthe air, upon encountering the blades 80 behaves in accordance with theprinciples of supersonic flow. One of such principles is that when thedirection of air flowing at supersonic velocities is changed, thischange is not gradual but occurs suddenly along a front or surface knownas a shock plane or shock surface. These shock planes may bephotographed due to the radical difference in density of the air on thetwo sides of the plane. It is also observed that the density on thedownstream side of the shock plane is greater than that on the upstreamside, and the ow velocity consequently lower.

The effect of the supersonic velocity encounter between the diffuserblade 80 and the discharging air from the impeller 22 is to firstproduce a shock plane identified in Figure 4 by the dotted line 84, theshock plane 84 being produced by the impact of the discharging airagainst the forward blade surface portion 85 between the leading edge ofthe blade 80 and the constriction point 81. After passing through theshock plane 84, the air is traveling in a direction indicated by thearrow 86, and upon encountering the adjacent blade at its rearwardsurface 87, again changes its direction as indicated by the arrow 88.Since the air is still traveling at supersonic velocity (relative to theblades 80), this second change of direction produces a second shockplane 89 which crosses the area between two adjacent blades atapproximately the constriction point 81.

It will be recalled that the velocity of the air is reduced each timethat it passes through a shock plane and the net result of passingthrough the .two shock planes 84 and 89 is to reduce the relativevelocity of the air in the diffuser passage to a Value near Mach 1.0.Therefore, the air thereafter behaves in accordance with Bernoullistheorem Aand the widening space between the adjacent diffuser blades 80results in further compression of the air.` Still further compression isachieved by the continual widening of the manifold passage within thehousing 40 as the air is carried to and discharged into the combustionchambers 50.

It has sometimes been found necessary, in order to initiate the iiow ofair through the compressor, to provide the manifold 75 connected bypassages 76 to the throat area of the diffuser 25. After the initialflow has been instituted, the pressure in the manifold 75 drops, thevalve 77 closes, and the operation thereafter proceeds in accordancewith the supersonic principles just described.

It will be realized by those skilled in the art that thecounter-rotation of the impeller 22 and the diifuser 25 may beaccomplished in various ways. For example, in stationary installations,a pair of electric motors may be employed to drive these two rotarymembers in opposite directions. Another method of achievingcounter-rotation is by the provision of two instead of one turbinewheel, such as that indicated by the reference character 60 in Figure 1.Two such turbine wheels can be provided with oppositely inclined bladeswhereby to rotate in opposite directions. One of the turbine wheels isthen mounted on a coaxial hollow shaft and connected to drive thediffuser rotor.

It is believed obvious, furthermore, that the principles of supersoniccompression involved in the foregoing construction are equallyapplicable to axial flow compressors. In such devices, a series ofcounter-rotating impellers and difusers can be arranged along an axis toaccomplish the same supersonic relative velocity as is produced in thediffuser of the centrifugal type of compressor illustrated herein.

While the compressor shown and described herein is fully capable ofachieving the objects and providing the advantages hereinbefore stated,it will be realized that it is capable of considerable modification bythose skilled in the art. Therefore, I do not mean to be limited to theform shown and described herein, but rather to the scope of the appendedclaims.

I claim:

l. In a Huid compressor of the class described, the combination of: arotatably mounted drive shaft; a lbladed impeller secured to a forwardend of said shaft for rotation therewith; a diiuser comprising a bodyrotatably mounted on said shaft adjacent said impeller and rearwardlythereof, and a plurality of blades on said body projecting forwardlytherefrom around the periphery of said impeller, said diffuser bladeshaving sharp leading edges and being inclined to the radius of saidimpeller and thickened at points therein opposite apoint in the nextadjacent blade intermediate the leading and trailing edges thereofwhereby to form a plurality of Venturi-like passages with convergingentrance sections between said blades; and drive means to rotate saidshaft and diffuser in opposite directions whereby air centrifugallydischarged from said impeller enters said Venturi passages at a relativevelocity above the speed of sound in air at the entrances of saidpassages.

2. A compressible iluid compressor comprising: a centrifugal fluidimpeller mounted for rotation on an axis to discharge fluid tangentiallyoutward from said axis; a diffuser having a coaxial rotor mountedadjacent said impeller and a plurality of blades on said rotorprojecting therefrom around the periphery of said impeller in th-e pathof fluid discharging as aforesaid, said blades each having sharp leadingedges and being inclined to a radius of said impeller and having athickened portion opposite a point in the next adjacent bladesubstantially to the rear of the leading edge thereof, whereby to form apassage between each adjacent pair of said blades with a constrictedthroat in said passage and a substantial converging section precedingsaid throat; and drive means to rotate said diffuser and impeller atsuch relative speed that compressible uid discharged as aforesaid fromsaid impeller enters said passages at a velocity relative thereto whichis above the speed of sound in the fluid in the region between saidimpeller and passages.

3. The construction of claim 2 further characterized by havingastationary wall adjacent said diifuser positioned to laterally enclosesaid passages, and starting pressure relief means including at least onecontrollable port in said wall to selectively release fluid from saidregion whereby to initiate ow of said fluid at said speed.

4. A compressible fluid compressor comprising: a centrifugal fluidimpeller mounted for rotation on an axis to discharge uid tangentiallyoutward from said axis; a diffuser having a coaxial rotor mountedadjacent said impeller and a plurality of blades on said rotorprojecting therefrom around the periphery of said impeller in the pathof Huid discharging as aforesaid, said blades each having a bulge formedon the advancing surface thereof, said bulge rising to a maximumthickness at a point opposite a point in the blade adjacent saidsurface, substantially to the rear of the leading edge thereof, wherebyto form a passage between each adjacent pair of said blades with aconstricted throat in said passage and a substantial converging sectionpreceding said throat; and drive means to rotate said diffuser andimpeller at such relative speed that compressible fluid discharged asaforesaid from said impeller enters said passages at a velocity relativethereto which is above the speed of sound in the iiuid in the regionbetween said impeller and passages.

5. A compressible uid compressor comprising: a lluid impeller mountedfor rotation on an axis to discharge Huid tangentially outward from saidaxis; a diffuser having a coaxial rotor mounted adjacent said impellerand a plurality of blades on said rotor projecting therefrom around theperiphery of said impeller in the path of fluid discharging asaforesaid, said blades each having sharp leading and trailing edges andeach being inclined to a radius of said impeller and each having athickened portion intermediate the leading and trailing edges thereof,whereby to form a passage between each adjacent pair of said blades witha constricted throat in said passage, said throat being positioned toprovide a substantial converging section preceding said throat, and asubstantial diverging section following said throat; and drive means torotate said diffuser and impeller at such relative speed thatcompressible iluid discharged as aforesaid from said impeller enterssaid passages at a velocity relative thereto which is above the speed ofsound in the Fluid in the region between said impeller and passages.

6. A compressible fluid compressor comprising: a centrifugal impeller; adiffuser having a coaxially mounted rotor adjacent said impeller andsharp edged blades on said rotor arranged in a circular seriessurrounding said impeller to provide a plurality of discharge passagesbetween adjacent pairs of said diffuser blades, said blades beingthickened intermediate their edges to provide converging entranceportions in said passages; means to rotate said impeller at apredetermined speed; and means to counter-rotate said rotor at a speedsuch that the relative periphery velocity of said impeller and diffuserblades at the point of closest proximity thereof is greater than thespeed of sound in said fluid in the region of said point.

7. The construction of claim 6 further characterized by having lateralwalls enclosing said passages and an initial pressure relief port in atleast one of said walls.

8. The construction of claim 7 further characterized by having apressure-responsive valve in said port to close the same when saidinitial pressure drops below a predetermined value. s.

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